XML 89 R66.htm IDEA: XBRL DOCUMENT v3.19.1
Securities Owned/Sold but Not Yet Purchased - Schedule of Securities Owned/Sold But Not Yet Purchased (Detail) - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities Owned Total $ 6,419 $ 8,873
Securities Sold, but not yet Purchased Total 1,338 1,698
Trading Securities [Member]    
Security Owned and Sold, Not yet Purchased, at Fair Value [Line Items]    
Securities Owned Total 6,419 8,873
Securities Sold, but not yet Purchased Total $ 1,338 $ 1,698